Robert Wagner I'm a Murder Suspect ... On TV

File this under bad timing ... actor Robert Wagner -- currently the target in the Natalie Wood death probe -- will play a murder suspect on "NCIS" tonight.

In the episode, 81-year-old Wagner -- who plays Michael Weatherly's father on the show -- is arrested after police find him in a car with a dead body in the trunk.

It's pretty ironic -- considering the real-life L.A. County Sheriff's Department just reopened a 30-year-old homicide investigation into the death of Wagner's wife Natalie Wood.

Wagner's not officially a suspect -- but there's no denying ... investigators are definitely looking into the possibility that Wagner was responsible for Wood's death.

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